After years of planning and tough talk, a string of electric cars that are actually going on sale - as opposed to being just concepts - will be on show when the Paris motor show opens to the public on Saturday.

Nissan is currently taking orders for its pure electric Leaf model, which has a range of 160km.

General Motors (GM) will start selling its plug-in electric car with a range-extending petrol engine within months.

And Toyota's plug-in petrol-electric Prius hybrid will go on sale next year.

But it is not clear which solution will appeal the most to car buyers, who are increasingly spoilt for choice.

So the automotive behemoths are fighting hard to convince consumers that theirs is the best way forward.

100% electric

Nissan and its partner Renault are the most vocal advocate of pure electric cars, insisting that in order to prevent global temperatures from rising by more than 2 degrees Celsius, car emissions must be reduced by 80-90% in all new vehicles.

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Nissan believes zero emission motoring is the answer

"The only way to do this is 100% electric motoring," Hideaki Watanabe, managing director of the Renault-Nissan Alliance's zero emission business, tells BBC News.

Mr Watanabe is dismissive of the solution offered by rivals Toyota and GM.

"Is a plug-in hybrid zero emission? No. And is the system cheap? No, since you've got two systems," he reasons.

Extended range

The world's two largest carmakers, in turn, insist electric cars are vastly inferior to plug-in hybrids because of their limited range.

But that is where their agreement ends.

GM's Ampera, named Volt in the US, is an electric car with a range of 60km.

The car, which will go on sale within months, is kitted out with a small petrol engine, which essentially acts as an electric generator that feeds power to the electric motor and tops up the batteries while driving - thus extending the range to more than 500km.

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The Ampera will be used as an electric car most of the time, GM says

"Our intention is that the majority of the driving in these vehicles is done with electrics only," explains Nick Reilly, president of GM Europe, in an interview with BBC News.

"But the beauty of the range extender is that when you do want to go on a longer journey, you can."

The range extender solution has become a popular choice with a number of supercar makers, including Jaguar which is showing a concept of a gas turbine-electric hybrid, and Fisker Automotive, which will start selling its Karma extended range electric vehicle next year.

"You may be able to get passion and beauty in an electric car, but you don't get freedom."

'More efficient'

Toyota's plug-in Prius, which will go on sale next year, offers a subtly different solution.

The car's range electric range is just 20km, which is enough to cover about 80% of drivers' daily needs, Didier Leroy, president of Toyota Motor Europe, tells BBC News.

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Toyota's solution is more efficient than those of rivals, Mr Leroy insists

Hence, there is less of a need to carry around a heavy and expensive battery, he reasons.

Once the battery is empty, the car operates like a conventional petrol-electric hybrid, which is much more efficient than the range extender, Mr Leroy insists.

Low emission cars

Electric motoring, in whatever form, is clearly becoming part of the automotive landscape, though all manufacturers agree that the internal combustion engine will remain the main source of power for cars for years, perhaps decades, yet.

Modern petrol and diesel engines are much less dirty than they used to be, however, with manufacturers being spurred on by ever-tighter emissions regulations across the world.

Visitors to the motor show will see masses of small cars that claim to emit less than 99 grammes of carbon dioxide per kilometre (g/km).

And even quite large crossover cars that resemble 4x4 vehicles often emit just 135g/km.

These cars represent impressive improvements made by the motor industry in recent years.

However, the Intergovernmental Panel on Climate Change stipulates that new cars must emit less than 45g/km on average to prevent global warming from running amok, Mr Watanabe says.